Process for roller-coating a bearing

ABSTRACT

A transfer roll rotates to have a coating liquid in a coating liquid tank filled in recesses formed on a roll surface thereof and to have a surplus coating liquid scraped off by a doctor blade, and rotates contacting with a coating roll. Thereby, the coating liquid in the recesses of the transfer roll is transferred to the coating roll. Thereafter, while the transfer roll is moved upward, an arm is rotated counterclockwise whereby the coating roll is separated from the transfer roll. The arm is further rotated whereby the coating roll is moved along an inner surface of a half bearing fixed to a jig and the coating roll applies the coating liquid to the inner surface of the half bearing.

BACKGROUND OF THE INVENTION

The present invention relates to a coated bearing manufacturing methodof and a coated bearing manufacturing apparatus for forming a coatinglayer on a bearing base material, and more particular, to a method ofand an apparatus for forming a coating layer on an inner surface of acylindrical-shaped or semicylindrical-shaped bearing base material withthe use of a coating roll.

Ordinarily, a coating layer of a coated bearing is formed by using acoating liquid obtained by mixing a thermosetting resin such aspolyimide resin (PI), epoxy resin, phenol resin, etc. with a solidlubricant such as molybdenum disulfide (MoS₂), graphite (Gr), etc. andapplying the coating liquid to an inner surface of a bearing basematerial.

Ways to apply a coating liquid to an inner surface of a bearing basematerial include a spraying method or a printing method. The sprayingmethod comprises jetting a coating liquid in a foggy manner from aspraying device to apply the same to an inner surface of a bearing basematerial and the printing method comprises using a pad or a roll toapply a coating liquid to an inner surface of a bearing base material.

JP-A-2001-304264 discloses a method of forming a coating layer on aninner surface of a half bearing in printing (referred below to asrolling printing), in which a roil is used. In the method, there areprovided a transfer roll, a coating roll (printing roll), and a backuproll. In order to form a coating layer, a coating liquid is firstdropped on a roll surface of a transfer roll and a coating roll isrotationally brought into contact with the transfer roll whereby thecoating liquid is transferred in uniform thickness to the coating roll.Succeedingly, a half bearing (bearing base material) is interposedbetween the coating roll and the backup roll and the both rolls arerotated. Thereby, the bearing base material passes between the bothrolls and in the passing process, the coating liquid on the coating rollis applied to an inner surface of the half bearing.

The spraying method involves a large dispersion in created filmthickness and an amount of a coating liquid, which is scattered andwasted, is much since the coating liquid is jetted in a foggy mannerfrom the spraying device. In the printing method, an amount of a coatingliquid wasted as in the spraying method can be made small. In theprinting method, in which a pad is used, however, a coating layer is badin thickness accuracy since the pad is pushed against an inner surfaceof a half bearing to apply a coating liquid thereto.

The printing method, in which a roll is used, shown in JP-A-2001-304264is excellent in thickness accuracy as compared with the pad printing. Inthe rolling printing method in JP-A-2001-304264, a transfer roll and acoating roll are rotationally brought into contact with each other, thatis, contact pressure between the transfer roll and the coating rollcauses a coating liquid to spread over a surface of the coating roll. Ina system, in which contact pressure between the both rolls causes acoating liquid to spread, however, it is difficult to control a coatingliquid to make the same constant in thickness over a whole periphery ofthe coating roll. Therefore, in the case where the coating liquid spreadover a surface of the coating roll is applied to an inner surface of ahalf bearing to form a coating layer, the coating layer is liable tobecome ununiform in thickness.

Also, in order to interpose a half bearing between a coating roll and abackup roll to apply a coating to an inner surface of the half bearing,it is necessary to separate; the coating roll from a transfer roll tomove the same near the backup roll. When the coating roll is separatedfrom the transfer roll, however, a coating liquid is drawn to a portionthereof, which has been in contact with the transfer roll, to stay therewith the result that there is caused a problem that in case of applyinga coating liquid to a half bearing, a coating layer becomes locally andpartially large in thickness.

SUMMARY OF THE INVENTION

The invention has been thought of in view of the situation and has itsobject to provide a coated bearing manufacturing method and a coatedbearing manufacturing apparatus, in which it is possible to uniformlytransfer a coating liquid to a surface of a coating roll and it ispossible to form a coating layer of uniform thickness on a bearing basematerial without generation of a portion, in which the coating liquidstays, on the coating roll when the coating roll and a transfer roll areseparated from each other.

The invention provides a coated bearing manufacturing method of applyinga coating liquid to an inner surface of a cylindrical-shaped orsemicylindrical-shaped bearing base material to form a coating layer,the method comprising: adhering the coating liquid to a roll surface ofa transfer roll, which roll surface is formed with a multiplicity ofrecesses, and using a doctor blade to remove a surplus coating liquidfrom the roll surface; thereafter rotating the transfer roll and acoating roll, while bringing the rolls into contact with each other, totransfer the coating liquid on the transfer roll to the coating roll;moving the coating roll relative to the transfer roll in a direction ofrotation of the coating roll in a region in contact with the transferroll while moving the transfer roll relative to the coating roll in aradial direction, which passes through a contact region of the transferroll and the coating roll; whereby the transfer roll and the coatingroll are separated from each other to terminate transfer of the coatingliquid to the coating roll from the transfer roll; and thereafterbringing the coating roll into contact with the inner surface of thebearing base material and moving the coating roll along the innersurface of the bearing base material while causing the coating roll torotate on its own axis in the state of contact, whereby the coatingliquid transferred to the coating roll is applied to the inner surfaceof the bearing base material to form the coating layer.

Also, the invention provides a coated bearing manufacturing apparatusfor applying a coating liquid to an inner surface of acylindrical-shaped or semicylindrical-shaped bearing base material toform a coating layer, the apparatus comprising: a transfer roll, a rollsurface of which is formed with a multiplicity of recesses; coatingliquid supply means, which supplies the coating liquid to the rollsurface of the transfer roll in a state, in which the transfer roll isrotated; a doctor blade, which removes a surplus coating from the rollsurface of the transfer roll; a coating roll, which rotates in beingcontact with the transfer roll to permit the coating liquid to betransferred thereto from the roll surface of the transfer roll;separation means, which moves the coating roll relative to the transferroll in a direction of rotation of the coating roll in a region incontact with the transfer roll while moving the transfer roll relativeto the coating roll in a radial direction, which passes through acontact region of the transfer roll and the coating roll, after transferof the coating liquid to the coating roll from the transfer roll,thereby separating the transfer roll and the coating roll from eachother; and revolution means, which causes the coating roll separatedfrom the transfer roll to contact with the inner surface of the bearingbase material and moves the coating roll along the inner surface of thebearing base material while causing the coating roll to rotate on itsown axis in the state of contact, thereby applying the coating liquidtransferred to the coating roll to the inner surface of the bearing basematerial to form the coating layer.

In the coated bearing manufacturing method and the coated bearingmanufacturing apparatus described above, the multiplicity of recessesare formed on the roll surface of the transfer roll. When the rollsurface of the transfer roll is immersed in the coating liquid in, forexample, a coating liquid reservoir, the recesses are filled with thecoating liquid. Thereafter, the doctor blade rubs against the rollsurface of the transfer roll to remove a surplus coating liquidtherefrom. Therefore, a state, in which the coating liquid adheresuniformly to the roll surface of the transfer roll, is brought about,and the coating liquid of uniform thickness spreads also over a surfaceof the coating roll, to which the coating liquid is transferred from thetransfer roll.

After the transfer roll and the coating roll rotate while being contactwith each other to have the coating liquid transferred to the coatingroll from the transfer roll, the coating roll is separated from thetransfer roll so as to apply the coating liquid to an inner surface of ahalf bearing. At this time, according to the invention, the coating rollis moved relative to the transfer roll in a direction of rotation of thecoating roll in a region in contact with the transfer roll while thetransfer roll is moved relative to the coating roll in a radialdirection, which passes through a contact region of the transfer rolland the coating roll, whereby the transfer roll and the coating roll areseparated from each other.

The following three configurations are conceivable as configurations, inwhich the both rolls are moved to realize the system of separation. Thefirst configuration is one (first configuration), in which both thetransfer roll and the coating roll are moved, the second configurationis one (second configuration), in which only the transfer roll is moved,and the third configuration is one (third configuration), in which onlythe coating roll is moved.

FIG. 5 shows the first configuration. In this configuration, assumingthat the transfer roll 1 and the coating roll 2 respectively rotate inan arrow A direction and in an arrow B direction, the transfer roll 1 ismoved in a radial direction (an arrow C direction) passing through acontact region S of the both rolls 1, 2 and the coating roll 2 is movedin a direction (an arrow D direction) of rotation of the both rolls 1, 2in the contact region S of the both rolls 1, 2. The coating roll 2 isdriven by the transfer roll 1 to rotate on its own axis.

In the first configuration of separation, the coating roll 2 is firstmoved (the arrow D direction) relative to the transfer roll 1 towardthat side of the roll surface, for which application of a coating liquidis finished, so that such movement does not lead to formation of a poolof the coating liquid on the roll surface of the transfer roll 1. On theother hand, in the case where the coating roll 2 is not moved towardthat side, for which application of the coating liquid is finished, butthe transfer roll 1 is moved in the radial direction (the arrow Cdirection), locations, in which the coating liquid stays locally, aregenerated on the roll surface of the transfer roll 1 and the rollsurface of the coating roll 2. Generation of such pool of the coatingliquid can be prevented by moving the coating roll 2 in the arrow Ddirection. Since the coating roll 2 is moved in the arrow D directionwhile rubbing slightly against the roll surface of the transfer roll 1,which moves in the arrow C direction, the coating liquid is broken welland less likely to be collected in the contact region S of the bothrolls 1, 2 due to the viscosity thereof.

FIGS. 6 and 7 respectively show the second and third configurations, inwhich only the transfer roll 1, or only the coating roll 2 is movedinstead of movements of the both rolls 1, 2 in the first configuration.The transfer roll 1 being moved obliquely upward as indicated by anarrow E in that case of FIG. 6, in which only the transfer roll 1 ismoved, and the coating roll 2 is moved obliquely downward as indicatedby an arrow F in that case of FIG. 7, in which only the coating roll 2is moved. In the second and third configurations in FIGS. 6 and 7, it ispossible to produce the same effect of preventing the coating liquidfrom staying as that in the first configuration.

The effect, produced by the recesses on the roll surface of the transferroll, of uniformly applying the coating liquid to the coating roll andthe effect, produced by the separating movements of the both rolls, ofpreventing the coating liquid from staying locally on the coating rollcombine together to enable the coating roll to form a coating layer ofuniform thickness on an inner surface of a bearing base material.

The respective recesses (called cell) on the roll surface of thetransfer roll comprise a very small one in the form of, for example, aquadrangular pyramid. Preferably, the recesses are not connected to oneanother but independent individually. Being independent, an amount of acoating liquid held in each recess is set constant. Thereby, a coatingliquid being transferred to the coating liquid can be made furtheruniform in thickness.

Preferably, a total content volume of the recesses on the transfer rollis 5 cm³/m² to 40 cm³/m². FIG. 8 is a graph indicating the relationshipbetween a total content volume of recesses per unit area of a transferroll and a film thickness of a coating layer in the case where a coatingliquid is transferred to a coating roll from a transfer roll and thenapplied to an inner surface of a half bearing by the coating roll toform a coating layer. It is understood from the graph of FIG. 8 thatuntil a total content volume of the recesses reaches around 5 cm³/m² to40 cm³/m², the film thickness of a coating layer can be controlled bychanging the total content volume of the recesses. When 40 cm³/m² isexceeded, a coating layer is not increased in film thickness even whenthe content volume increases, and a predetermined thickness results, sothat a total content volume of the recesses preferably has an upperlimit of 40 cm³/m².

When a coating liquid is transferred to a coating roll from a transferroll, the coating roll preferably rotates while being in contact withthe transfer roll over one or more revolutions. The coating roll ispushed against the transfer roll at an appropriate pressure to rotatemutually whereby a coating liquid is transferred to the coating rollfrom the recesses on a roll surface of the transfer roll. At this time,the coating roll makes one or more revolutions whereby a coating liquidis transferred uniformly to the coating roll further favorably. That is,the reason for this is that in the case where a coating liquid isprovisionally transferred from the transfer roll in a first revolutionof the coating roll and a region, in which the coating liquid is thin inthickness, is generated on a surface of the coating roll, the coatingliquid is transferred to such region from the transfer roll insubsequent revolutions and the coating liquid on the surface of thecoating roll is made uniform in thickness.

A roll surface of a coating roll preferably has a hardness of Hs 30 to80. Half bearings are designed to have necessary dimensions and assume anecessary shape in a state of being assembled to a housing of aconnecting rod or the like with a predetermined clamping force.Therefore, preferably, a roll surface of a coating roll is elasticallydeformed to absorb dispersion of individually different half bearings insurface shape according to circumstances. By having a roll surface of acoating roll having a hardness of Hs 30 to 80, a coating roll can absorbsuch dispersion of half bearings in surface shape, thus enablingcontributing to making a coating layer uniform in film thickness.

Further, when a coating liquid is applied to a half bearing by a coatingroll, the half bearing is preferably fixed to a jig. Provided that ahalf bearing is fixed to a jig, the half bearing can be put in a stablestate and a coating liquid can In the same state as that, in which ahalf bearing is fixed to a housing, so that such fixation contributesfurther to making a coating layer uniform in film thickness.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view showing an outline construction of a coating apparatusaccording to an embodiment of the invention;

FIG. 2 is a perspective view simply showing a coating liquid tank;

FIG. 3A is an enlarged view showing a roll surface of a transfer roll indevelopment;

FIG. 3B is a cross sectional view of the roll surface of the transferroll;

FIG. 4 is a side view showing a half bearing;

FIG. 5 is a schematic view showing a first configuration of a separatingmotion of the transfer roll and a coating roll;

FIG. 6 is a schematic view showing a second configuration of aseparating motion of the transfer roll and a coating roll;

FIG. 7 is a schematic view showing a third configuration of a separatingmotion of the transfer roll and a coating roll; and

FIG. 8 is a graph indicating the relationship between a total contentvolume of recesses per unit area of a roll surface and a film thicknessof a coating layer.

DESCRIPTION OF THE PREFERRED EMBODIMENT

An embodiment of the invention will be described below with reference toFIGS. 1 to 4. As shown in FIG. 4, according to the embodiment, anobject, to which a coating liquid is applied, is a half bearing 5 formedby lining a bearing alloy layer 4 of Cu or Al on an inner surface of aback metal layer 3. A coating apparatus 6, by which the coating liquidis applied to an inner surface of the half bearing 5, is shown in FIG. 1and mainly comprises a transfer roll 1 and a coating roll 2.

The transfer roll 1 is provided in a fixed position and rotationallydriven in a predetermined speed about an axis 1 a in an arrow Adirection by a motor (not shown). A multiplicity of recesses, forexample, recesses 7 in the form of a quadrangular pyramid shown in FIGS.3A and 3B, in which recesses the coating liquid stays, are formed on aroll surface of the transfer roll 1 to be arranged adjacent to oneanother axially and circumferentially. The recesses 7 are independent ofone another and no passages are present to connect between the recesses7. The recesses 7 are set to have a length and a width, respectively, inthe order of 50 μm to 500 μm and a depth in the order of 15 μm to 120μm, and its total content volume is 5 cm³/m² to 40 cm³/m². A totalcontent volume of the recesses 7 per unit area is appropriatelydetermined in the range described above according to a film thickness ofa coating layer applied to an inner surface of the half bearing 5.

A coating liquid tank 8 is juxtaposed to the transfer roll 1. As shownin FIG. 2, a side of the coating liquid tank 8 toward the transfer roll1 is opened. End surfaces 8 a, 8 a of both side walls on the left andright of the side thus opened are formed to make concavely curvedsurfaces having the same curvature as that of the roll surface of thetransfer roll 1. Also, a bottom surface of the coating liquid tank 8 isformed of, for example, a thin metallic sheet 9. A tip end of the thinsheet 9 is protruded slightly from end surfaces 8 a, 8 a of the sidewalls of the coating liquid tank 8.

The coating liquid tank 8 functions as coating liquid supply means, fromwhich the coating liquid is supplied to the transfer roll 1, and theconcavely curved surfaces 8 a, 8 a are in contact with the roll surfaceof the transfer roll 1 as shown in FIG. 1. Accordingly, the opened sideof the coating liquid tank 8 is configured to be closed by the transferroll 1 and the roll surface of the transfer roll 1 is put in a state ofbeing immersed in a coating liquid stored in the coating liquid tank 8.Also, the tip end of the thin sheet 9 is put into contact with the rollsurface of the transfer roll 1 and is elastically deformed downwardly.The tip end of the thin sheet 9 functions as a doctor blade 10, which iscaused by its own elastic restoring force to come into pressure contactwith the roll surface of the transfer roll 1 to remove a surplus coatingliquid from the roll surface when the transfer roll 1 rotates.

A liquid, for example, in which a solid lubricant is contained in a baseresin and then it is diluted with an organic solvent is used as acoating liquid stored in the coating liquid tank 8. In addition, used asa base resin are thermosetting resins such as polyimide (PI), epoxyresin, phenol resin, etc., or a heat resistant resin such as polyamideimide (PAI), polybenzimidazole (PBI), etc. Also, used as a solidlubricant are molybdenum disulfide (MoS₂), graphite (Gr),polytetrafluoroethylene (PTFE), tungsten disulfide (WS₂), boron nitride(BN), etc. Preferably, the coating liquid is regulated to have aviscosity of 200 m·Pa/sec to 3000 m·Pa/sec, more preferably, 500m·Pa/sec to 2000 m·Pa/sec.

The transfer roll 1 is made integral with the coating liquid tank 8 andmoved vertically together with the coating liquid tank 8 by an elevatingdevice. According to the embodiment, the transfer roll 1 rotates notonly at the time of ascent and descent but also at all times and suchrotation agitates the coating liquid stored in the coating liquid tank8. Owing to the agitation, the coating liquid is generally maintained ina homogeneous state without generation of demixing.

On the other hand, a roll surface of the coating roll 2 is finished tobe made a smooth surface. The coating roll 2 is rotatably supportedbelow the transfer roll 1 by a shaft 2 a at a tip end of an arm 12capable of circular motion (orbital motion) about a shaft 11. A rotatingdevice (not shown) causes the arm 12 to perform the circular motion. Ina state, in which the arm 12 revolves right above, the roll surface ofthe coating roll 2 comes into contact at a predetermined pressure withthe roll surface of the transfer roll 1. The roll surface of the coatingroll 2 is formed from, for example, a relatively soft plastic to have ahardness of Hs 30 to 80. In addition, the arm 12 performs the circularmotion with a motor (not shown) as a drive source to have the coatingroll 2 perform the orbital motion.

A jig 13 is arranged below the shaft 11 of the arm 12. The half bearing5 is detachably fixed to a semi-circular recess 13 a of the jig 13. In astate, in which the half bearing 5 is fixed to the jig 13, the rollsurface of the coating roll 2, which is caused by the arm 12 to performthe circular motion (orbital motion), comes into contact with an innerperipheral surface of the half bearing 5. When the coating roll 2 comesinto contact with the inner peripheral surface of the half bearing 5,the coating roll 2 is acted by torque to revolve while rotating on itsown axis.

The elevating device, which moves the transfer roll 1 up and down, andthe rotating device, which causes the coating roll 2 to perform thecircular motion, function as separation means for separating thetransfer roll 1 and the coating roll 2, as understood from the followingdescription. Also, the rotating device functions as revolving means,which moves the coating roll 2 along the inner surface of the halfbearing 5.

Subsequently, an operation in the case where the coating apparatus 6 isused to apply a coating liquid to the inner surface of the half bearing5 will be described. First, the coating liquid is stored in the coatingliquid tank 8. Also, the half bearing 5 is fixed to the jig 13. Thetransfer roll 1 is stopped at a lowermost position and the arm 12 isstopped at a position, in which it is turned vertically upward, to bringthe coating roll 2 into contact with a lower side of the transfer roll1. The transfer roll 1 is being rotationally driven by a motor (notshown) and when the coating roll 2 comes into contact with the transferroll 1, the coating roll 2 receives torque from the transfer roll 1 torotate.

Out of the transfer roll 1 and the coating roll 2, which are incontacting rotation, the transfer roll 1 is immersed in the coatingliquid stored in the coating liquid tank 8, so that the recesses 7 arefilled with the coating liquid. When that part of the recesses 7 of thetransfer roll 1, which is filled with the coating liquid, rotates in thearrow A direction and is exposed downward from the coating liquid tank8, the doctor blade 10 scrapes off a surplus coating liquid on the rollsurface (coating liquid adhering process).

The coating roll 2 comes into contact with the roll surface of thetransfer roll 1, from which the surplus coating liquid is scraped off,to rotate whereby the coating liquid in the recesses 7 is transferred tothe coating roll 2. Even if the coating liquid just after transferred tothe coating roll 2 is made concave-convex in shape under the influenceof the recesses 7, such irregularity immediately disappears due tofluidity thereof and the coating liquid defines a smooth surface, whichfollows the roll surface of the coating roll 2.

When the transfer roll 1 and the coating roll 2, respectively, make oneor more revolutions and the coating liquid is uniformly transferred tothe roll surface of the coating roll 2, the transfer roll 1 issubsequently moved upward (an arrow C direction) by the elevating device(not shown). The arm 12 begins to rotate counterclockwise in FIG. 1 in amanner to interlock with the upward movement of the transfer roll 1.

Owing to rotation of the arm 12, the coating roll 2 is moved in an arrowD direction along a tangent line at a contact region S of the both rolls1, 2. Thereby, the coating roll 2 is moved in the same direction as thatof rotation thereof relative to the transfer roll 1, which is separatingupward therefrom, so that the coating roll 2 separates from the transferroll 1 without generation of a pool of the coating liquid, in which thecoating liquid is increased locally in thickness, on the roll surfacethereof (separation process). Therefore, the coating liquid transferredto the roll surface of the coating roll 2 forms a coating liquidtransfer film having a uniform thickness over a whole periphery thereof.

After the coating roll 2 is separated from the transfer roll 1, the arm12 also rotates counterclockwise. Thereby, the coating roll 2 comes intocontact with the Inner surface of the half bearing 5, which is fixed tothe jig 13. Then, the coating roll 2 moves along the inner peripheralsurface of the half bearing 5 while rotating on its own axis, so thatthe coating liquid on the roll surface of the coating roll 2 is appliedto the inner peripheral surface of the half bearing 5 to form a film asa coating layer (coating process). Thereafter, the arm 12 turns up to astate, in which it faces just upward, and brings the coating roll 2 intocontact with the transfer roll 1, which descends to the lowermostposition, to prepare for application of the coating liquid to asubsequent half bearing 5.

That half bearing 5, to an inner surface of which the coating liquid isapplied, is removed from the jig 13 and conveyed to a drying oven and akiln in order where drying and baking of a coating layer are carriedout.

In this manner, according to the embodiment, it is possible to uniformlytransfer the coating liquid to the roll surface of the coating roll 2,thus enabling forming a coating layer of uniform thickness on the halfbearing 5. In order to confirm the effect of the invention, theinventors of the present application have made measurements with respectto the case where (product of embodiment) a coating layer is formed bythe invention and the case where (product of comparison) a coating layeris formed by a conventional method. The following TABLE 1 indicatesresults of measurements on the product of embodiment and the product ofcomparison.

TABLE 1 uneven film thickness portion end (a) center (c) end (b)  (μm)product of 5 5 5 None embodiment product of 2 5 2 8 comparison

The conventional method is the same as that described inJP-A-2001-304264 and as follows. That is, a coating liquid is firstsupplied to a roll surface of a transfer roll, the transfer roll and acoating roll are caused to rotate in contact with each other, and thecoating liquid is caused to uniformly spread on a surface of the coatingroll. Thereafter, the coating roll is separated from the transfer rollto interpose a half bearing between it and a backup roll, and thecoating roll and the backup roll are rotated to apply the coatingliquid, which spreads on the surface of the coating roll, to an innersurface of the half bearing.

In TABLE 1, locations, in which measurements of film thickness are made,on a half bearing 5 in FIG. 4 include an end (a) in a location (a) nearto one end in a circumferential direction, a center (c) in a location(c) centrally in the circumferential direction, and an end (b) in alocation (b) near to the other end in a circumferential direction. Also,measurements of film thickness are made wholly in the circumferentialdirection and locations, in which changes in film thickness are large,are represented as uneven portions in terms of differences of filmthickness between maximum and minimum dimensions.

As seen from TABLE 1, the product of comparison is small in filmthickness in the locations (a), (b) near the both ends as compared withthe center thereof. The reason for this is that when interposition, of ahalf bearing between the coating roll and the backup roll begins andwhen the half bearing leaves from between the both rolls, a contact areabetween the coating roll and the half bearing is small and contactpressure is varied, so that a tendency, in which the film thicknessdecreases, exhibits itself. Also, an uneven portion is considerablyvaried in film thickness, which seems that a pool or pools of thecoating liquid are generated on the coating roll to form the unevenportion.

In contrast, with the product of embodiment, locations (a), (b) near toboth ends of a half bearing can be made equivalent in film thickness tothat in a center (c) and no uneven portion is generated, from which itis understood that the coating method according to the invention isexcellent in formation of a coating layer having a uniform thickness.

In addition, the invention is not limited to the embodiment describedabove and shown in the drawings but the following extension or changesare possible.

The transfer roll 1 and the coating roll 2 may be separated from eachother by moving only the transfer roll 1 obliquely upward as shown inFIG. 6, or moving only the coating roll 2 obliquely downward as shown inFIG. 7.

A bearing base material, to which a coating liquid is applied, may becylindrical-shaped. In such e, it suffices to enable the coating roll 2to move together with the arm 12 also along the shaft 11, which axialmovement causes the coating roll 2 and the arm 12 to be arranged in thecylindrical-shaped bearing and makes the arm 12 perform a circularmotion.

1. A coated bearing manufacturing method of applying a coating liquid toan inner surface of a cylindrical-shaped or semicylindrical-shapedbearing base material to form a coating layer, the method comprising:adhering the coating liquid to a roll surface of a transfer roll, whichroll surface is formed with a multiplicity of recesses, and using adoctor blade to remove a surplus coating liquid from the roll surface;thereafter rotating the transfer roll and a coating roll, while bringingthe rolls into contact with each other, to transfer the coating liquidon the transfer roll to the coating roll; moving the coating rollrelative to the transfer roll in a direction of rotation of the coatingroll in a region in contact with the transfer roll while moving thetransfer roll relative to the coating roll in a radial direction, whichpasses through a contact region of the transfer roll and the coatingroll, whereby the transfer roll and the coating roll are separated fromeach other to terminate transfer of the coating liquid to the coatingroll from the transfer roll; and thereafter bringing the coating rollinto contact with the inner surface of the bearing base material andmoving the coating roll along the inner surface of the bearing basematerial while causing the coating roll to rotate on its own axis in thestate of contact, whereby the coating liquid transferred to the coatingroll is applied to the inner surface of the bearing base material toform the coating layer.
 2. The coated bearing manufacturing methodaccording to claim 1, wherein the multiplicity of recesses formed on theroll surface of the transfer roll have no passages connecting oneanother.
 3. The coated bearing manufacturing method according to claim1, wherein the multiplicity of recesses formed on the roll surface ofthe transfer roll have a total content volume of 5 to 40 cm³/m².
 4. Thecoated bearing manufacturing method according to claim 1, wherein whenthe coating liquid on the transfer roll is to be transferred to thecoating roll, the coating roll makes one or more revolutions contactingwith the transfer roll.
 5. The coated bearing manufacturing methodaccording to claim 1, wherein the roll surface of the coating roll has ahardness of Hs 30 to
 80. 6. The coated bearing manufacturing methodaccording to claim 1, wherein the coating roll applies the coatingliquid to the bearing base material put in a state of being fixed to ajig.